1. Field of the Invention
The present invention relates to a magnetic head and a manufacturing method thereof, and more particularly to a magnetic head used to record an information signal in a narrow track being formed on a magnetic recording medium at the same time and to reproduce the information signal from the narrow track, and a manufacturing method thereof.
2. Description of the Prior Art
In the prior art, the magnetic head of this type is manufactured by a so-called butt method in which two head core members are butted with a gap member being interleaved therebetween.
FIGS. 1A-1E show an example of the manufacturing method of the magnetic head by the conventional butt method An ingot 1 of oxide magnetic material such as Mn--Zn ferrite shown in FIG. 1A is cut and ground into a magnetic material block 2 shown in FIG. 1B. A groove 3 for a winding shown in FIG. 1C is formed in the block 2 by grinding and the like, then a gap surface 4 is polished to finish it into a smooth surface. The block 2 which is one of the core members and a block 2' which is the other core member are made to face each other with a gap spacer member 5 of a non-magnetic material being on the gap surface 4, and they are fixed to each other by a bond 6 such as glass as shown in FIG. 1D. The assembly is sliced to a predetermined thickness as shown by broken lines in FIG. 1D and the slice is polished to form a magnetic head element shown in FIG. 1E. In the prior art manufacturing method of the magnetic head described above, machining work is necessary to cut and grind the gap surface 4 in order to form the required head gap. However, as a result of such machining work, the magnetic characteristic of the magnetic material is deteriorated, by the break of the magnetic material or the strain caused by the machining, and the head gap meanders or the bond at the head gap diffuses into the magnetic material so that the head gap becomes unstable. Accordingly, it is very difficult in this method to improve an electro-magnetic transducing characteristic of a magnetic head having a head gap length (referred as Gl hereinafter), Gl of smaller than 30 .mu.m corresponding to the track width, and to mass-produce such magnetic heads.
FIGS. 2A-2I show another example of the conventional manufacturing method of the magnetic head of this type. A magnetic material plate 12 shown in FIG. 2B is placed on a reinforcing plate 11 such as a crystalized glass shown in FIG. 2A, and another reinforcing plate is placed thereon to form a three-layer lamination 13 as shown in FIG. 2C. The lamination 13 is cut along broken lines shown in FIG. 2C to form blocks 14, which are stacked one on the other as shown in FIG. 2D, and the stacked blocks 14 are cut along broken lines shown in FIG. 2D to form block halves 15. A groove 16 for a winding is formed in one of a pair of block halves as shown in FIG. 2F, and a gap spacer 18 of a non-magnetic material is attached to a gap surface 17 as shown in FIG. 2G. Then, the block half 15 and the block half 15' are butted and joined together as shown in FIG. 2H. The block is then polished and sliced to an appropriate thickness to form magnetic heads shown in FIG. 2I.
This method of manufacturing the magnetic head has the same problem in the head gap forming surface as that encountered in the method of FIG. 1. In addition, it is difficult to align the tracks (align the magnetic material member of the block half 15' to the magnetic material member of the block half 15).
FIG. 3A-3D show another example of the conventional manufacturing method of the magnetic head which was proposed to resolve the above problem. A hole 22 is previously formed in a head substrate 21 as shown in FIG. 3A, a magnetic material core member 23 such as Sendust alloy is deposited on the substrate 21, and a gap member 24 of a non-magnetic material such as SiO.sub.2 having a predetermined thickness is deposited on one surface of the magnetic material core member 23, that is, a gap forming surface, as shown in FIG. 3B. A magnetic material thin film 25 such as Sendust is deposited on another magnetic material core member by sputtering as shown by an arrow a in FIG. 3B, and the magnetic material thin films 25 deposited to undesired areas are removed to form a head block shown in FIG. 3C.
In this manufacturing method, the problem encountered in the butt method is resolved but the following new problem arises. In this method, it is H) necessary to form the aperture 22 (FIG. 3A) for the winding in the magnetic head substrate 21. However, when the magnetic head having a small Gl such as smaller than 20 .mu.m is to be manufactured, the shape of the small aperture significantly affects a recording/reproducing efficiency of the magnetic head. Accordingly, it is required to very precisely form the aperture having .theta.=60.degree., l.sub.1 =0.4 mm and l.sub.2 =0.35 mm as shown in FIG. 3A. The magnetic head substrate 21 must be made of a substrate material such as partially crystallized glass which has the equal thermal expansion coefficient to that of the magnetic material thin films 23 and 25 deposited by sputtering, shows a good compliance to a magnetic recording material such as a magnetic tape and has a high abrasion resistance. It is almost impossible to precisely form the aperture of FIG. 3A in the substrate 21 of such material. It may be possible to drill a round hole by an ultrasonic machine and shaping the hole by a grinding stone, but this is far from practical.
FIG. 3 shows a sectional view after the magnetic material thin film has been deposited to the intermediate member shown in FIG. 3B. As shown in FIG. 3D, the magnetic material thin film 25 deposited by sputtering causes a step coverage, that is, an insufficiently deposited area as shown by an arrow b.